400 Senhor Capello — Kew and Lisbon Magnetic Curves [May 28, 



In the paper quoted above, the authors have also shown, — 

 1 st. That all the small peaks in the Kew curves are simultaneously re- 

 produced in the Lisbon curves in the same sense in the declination and 

 bifilar, but in a contrary direction in the vertical force. 



2nd. That, generally, all the waves of the declination and bifilar at Kew 

 were reproduced in the corresponding Lisbon curves, sometimes more or 

 less disfigured. 



3rd. That in the generality of cases, with the exception of peaks and 

 hollows, in which they are opposed, the vertical-force curves of the two 

 stations do not resemble each other. 



Let us now see if these laws are confirmed in these disturbances. 



First Disturbance. — This series of disturbances commenced at Lisbon, 

 February 20th 16'^ 12"" G. M.T., by a sudden increase of the declination, 

 and an enormous diminution of the vertical force. The horizontal force 

 likewise decreased rapidly, but IS'"" later (16^ 25"") : this is noteworthy. 

 However, the three elements, and especially the horizontal force, had been 

 somewhat disturbed since 10^ 2/"^ G. M. T. 



It is noticeable, in the large diminution of vertical force, that although 

 the curve in descending ran off the edge of the paper, we can fix the point 

 of minimum (approximately), which gives us a little more than 0*1 

 (English units) as the value of the disturbance. The increase in dechna- 

 tion was nearly a degree (59'*3), and the diminution of horizontal force 

 0-052 Enghsh units. 



This last diminution commenced, as we have before stated, 13™ later than 

 the other disturbances ; and the time of minimum is also 6"^ to S'"" after 

 the corresponding points of declination and vertical force. 



In other respects the remaining waves of the horizontal force do not 

 agree with those of the declination and vertical force. 



The Kew curves agree tolerably well with the Lisbon curves, up to the 

 time of the large and rapid movements. Here it appears that the large 

 movements of the three instruments were of the same nature as the 

 Lisbon ones ; and it is very possible that the large variations were 

 more considerable and rapid, since they failed to record their traces on the 

 paper. 



These large movements seem to have begun in the three instruments at 

 Kew at the same time (16'' 30°"), at which time the Lisbon declination and 

 vertical force had deviated to half their full extent. 



The small peaks are reproduced at the two stations at the same absolute 

 time, the two vertical forces being always in opposite directions. 



The fix&t period of this disturbance seems, therefore, to be of the same 

 nature in the two stations, i. e. the disturbing forces have acted on the 

 three instruments in a similar manner. 



Second Disturbance. — Let us now pass to the second period. 



The large movements have ceased, but the horizontal force remains too 

 low, and in continual vibration. Towards 2^ and 3^ of the 21st of February 



